layer
n. countablen. a single thickness of something that covers a surface or sits between other things. You can think of it like the different parts of a cake or the clothes you wear on a cold day.
n. a single thickness, coat, or stratum of material covering a surface or forming a component of a tiered structure. Often used to describe physical strata or conceptual levels of complexity.
The cake has a thick layer of chocolate cream.
To stay warm while hiking, you should wear a base layer that wicks away moisture.
The geologist explained that each distinct layer of sediment represents a different era in the planet's environmental history, preserved through millions of years of pressure.
Appears at first glance to be from Middle English leyer, leyare (“a layer of stones or bricks”), equivalent to lay + -er. In which case, ultimately identical to etymology 2 below. For the pronunciation compare prayer. However, this word layer (referring to a thickness of a material covering a surface) has also been argued to be from a respelling of an obsolete sense of the word lair that was once used by farmers, which had to do with soil. The connecting sense between the usual meaning of lair and the specialised farming meaning was: an area where cows typically rest, the ground being fertilised by their waste. Related to lie, ledger.
From lay + -er.
Commonly used with the preposition 'of' to specify the material or substance.